Conventionally, a typical automotive upholstery component, which is suitable for use on the inner wall surface of vehicle body panels, consists of a laminated assembly of a resin core member and a surface skin member. The resin core member is molded into a desired shape, and is provided with a sufficient rigidity to retain its shape, and to be securely mounted on the vehicle body panel. The surface skin member is provided with a suitable cushioning property.
In recent years, the resin core member is given with increasingly complicated, three-dimensional shapes, and the molding process known as a mold press forming process has been widely used for producing such resin core members. To simplify the molding process, the surface skin member is often attached to the surface of the resin core member simultaneously as the resin core member is molded into a desired shape.
FIG. 12 illustrates a typical conventional arrangement for molding an assembly consisting of a resin core member and a surface skin member. First of all, a surface skin member 3 is placed on a surface skin retaining frame 2 of an upper die half 1 of a mold press forming die assembly, and the upper die half 1 is lowered along with the surface skin retaining frame 2. As illustrated in FIG. 13, when a certain gap is defined between the upper die half 1 and a lower die half 4 of the die assembly, molten resin M for forming a resin core member is distributed over the die surface of the lower die half 4 from an injection molding device 5 connected to the lower die half 4. Thereafter, as illustrated in FIG. 14, the two die halves 1 and 4 are closed upon each other so that a resin core member 6 is mold press formed into a prescribed shape while the surface skin member 3 is integrally attached to the surface of the resin core member 6.
The parting line of the die assembly normally lies on a single plane, but modern vehicle design requires highly complex upholstery components which involve three-dimensional parting lines as shown in FIG. 15. In such a case, a gap h is created between the general parting line a and the special parting line b as illustrated in FIG. 16. Because the parting line thus does not lie on a single plane and, in particular, because the surface skin retaining frame 2 is spaced from the special parting line b, the part of the surface skin member 3 adjoining the special parting line b tends to be excessively stretched during the molding process with the result that parts of the surface skin member 3 may be excessively stretched, thinned or whitened or may be even ruptured. Even when such catastrophic results are avoided, due to the excessive tension applied to the surface skin member 3, the spring back of the surface skin member 3 may cause warping or other deformation to the resin core member 6 attached thereto with the result that undesirable gaps may be created between the laminated assembly, and the vehicle panel member or the laminated assembly may interfere with adjoining components.